ACL 5500 Installation Manual page 4

APPLICATION
THEORY OF
OPERATION
The ACL 5500 Combustion Safety controller is designed to ignite and prove a
continuous pilot while monitoring and annunciating multiple heater shutdowns for
all types of gas fired heaters and industrial sized burner applications.
The ACL 5500 utilizes a single ignitor/flame rod to provide both flame
acknowledgment and ignition at the pilot tip. When the ACL 5500 starts its
ignition sequence, fuel gas travels to the pilot tip where the ignitor/flame rod is
located and sparking. Once the gas is lit, the flame becomes a current path for
flame acknowledgment and the unit stops sparking. After the pilot has been
proven for 20 seconds (factory set) the ACL 5500 will allow gas to the main
burner.
If the pilot flame is extinguished, the current path is broken and the ignitor/flame
rod starts sparking within 1 second to attempt to re-light the pilot. The main is
shut off during this re-light period. If a flame is not established within the 5
second sparking period, the controller will immediately drop the output to
solenoid #1 pilot gas valve. The controller will attempt to light 2 more times with
15 seconds between each trial when equipped with three trial module. If the
flame is still not lighting, the flame fail will then be displayed on the annunciation
panel.
If any of the shutdowns are tripped, the controller will not attempt any re-light,
solenoid outputs will de-energize immediately and that specific shutdown will
then be indicated on the annunciation panel. The shutdown must be cleared
before the controller will allow an ignition cycle.
In an application where the ACL 5500 is used to ignite and monitor two burners,
ignition will occur at both pilots simultaneously when a start is initiated. If a
flame is not established at both pilots during the 5 second trial for ignition the
solenoid #1 outputs will drop out closing both pilot valves and a flame fail will be
indicated on the annunciator panel (slow flash for pilot #1 and quick flash for pilot
#2). If both pilots have been proven for a period of 20 seconds solenoid #2
outputs will be energized allowing the main burner valves to open. During
normal operation should either pilot be extinguished there will be a 5 second trial
for re-ignition at that pilot, and the main solenoid outputs will be shut off during
the trial for ignition period. If a flame is not re-established during the 5 second
period the remaining pilot solenoid output will be de-generized closing the pilot
gas outputs immediately and will not attempt any re-light. The specific shutdown
will then be indicated on the front annunciator panel. The shutdown must be
cleared before the controller will allow an ignition cycle.
ACL 5500 Combustion Safety Controller ACL 5500 Combustion Safety Controller
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